One approach to minimizing the negative consequences of excessive gambling is staff training to reduce the rate of the development of new cases of harm or disorder within their customers. The primary goal of the present study was to assess suitable benchmark criteria for the training of gambling employees at casinos and lottery retailers. The study utilised the Delphi Method, a survey with one qualitative and two quantitative phases. A total of 21 invited international experts in the responsible gambling field participated in all three phases. A total of 75 performance indicators were outlined and assigned to six categories: (1) criteria of content, (2) modelling, (3) qualification of trainer, (4) framework conditions, (5) sustainability and (6) statistical indicators. Nine of the 75 indicators were rated as very important by 90 % or more of the experts. Unanimous support for importance was given to indicators such as (1) comprehensibility and (2) concrete action-guidance for handling with problem gamblers, Additionally, the study examined the implementation of benchmarking, when it should be conducted, and who should be responsible. Results indicated that benchmarking should be conducted every 1–2 years regularly and that one institution should be clearly defined and primarily responsible for benchmarking. The results of the present study provide the basis for developing a benchmarking for staff training in responsible gambling.